Some agricultural tractors have two pedal brake systems so that left/right differential braking can be used to assist in turning the tractor. EU agricultural tractor brake regulations require that differential braking be disabled when the tractor is moving at higher transport speeds. Mechanical manual pedal locks have been used on such two pedal brake systems to disable differential braking by manually locking the brake pedals together. It is desirable to have an automatic means of disabling differential braking. But, mechanically locking the brake pedals together is difficult to automate. Additionally, a mechanical pedal lock does not insure that brake pressures are equal on the right and left sides of the rear axle, as slop in the pedal lock and pedal assembly flex can cause a brake pressure differential.